I can't vouch for the person who posted the 400, but the world record for 24 hours is at least 521. With that being their first posting, chances are that it was just an error. They could have easily typed in 40, not realizing that the zero that is already there was still there. Now the overall leader riding at least 200 miles per day is definitely legitimate. Just type his name in a search engine, and you will find not only his website, where he is attempting to break the 1 year biking record of just over 75,000 miles, but you will find impressive results for him in ultra distance cycling races as well.